Pharmaceutical excipients play a crucial role in the development of solid oral dosage forms. Excipients influence the processability of the powders and granulates used to form solid oral dosage forms, and are selected to assure uniform weights and drug content among unit doses within and among batches. Excipients also influence numerous physical properties of a drug dosage form, including hardness, friability, and ease of disintegration/dissolution. Excipients also influence the bioavailability of a drug when orally ingested by impacting the rate at which the product dissolves in the gastrointestinal tract, the solubility of the drug in the gastrointestinal tract, and the portion of the GI tract in which the drug is released.
When rapid bioavailability is desired, preferred modes of administration include parenteral, inhalation, mucosal and buccal administration. Tablets and capsules are generally available only in immediate release, extended release, and delayed release formats, and are not typically employed when rapid bioavailability is desired because of the time it takes for the dosage form to dissolve, and the resulting delay in gastrointestinal absorption. The present inventors recently proposed in PCT/EP97/02709 (published as WO 97/44023) a novel delivery system for orally delivering diclofenac that employed an alkali metal bicarbonate to accelerate the bioavailability of diclofenac from numerous oral dosage forms, including tablets, powders for dissolution in water, gum, chewable tablets, and liquids, among others. The current application claims priority to WO 97/44023 and incorporates the application's contents by reference.
Currently marketed forms of diclofenac tablets contain various pharmaceutical excipients. For example, diclofenac sodium 25 mg film-coated tablets marketed by Novartis Healthcare as Novapirina® contain colloidal silica, cellulose, lactose, magnesium stearate, polyvidone, sodium carboxymethylcellulose, hydroxypropylmethylcellulose, polysorbate, talc, and titanium dioxide.
Diclofenac potassium 50 mg film-coated tablets marketed variously as Cataflam,® Voltfast,® and Voltaren® Rapid contain calcium phosphate, saccharose, maize starch, talc, sodium carboxymethylcellulose, colloidal anhydrous silica, polyvinylpyrrolidone, microcrystalline cellulose, magnesium stearate, polyethylene glycol, titanium dioxide, and iron oxide red.
Diclofenac potassium 12.5 mg film-coated tablets marketed as Voltaren Dolo® contain colloidal anhydrous silica, lactose, maize starch, sodium starch glycolate, polyvidone, magnesium stearate, microcrystalline cellulose, hydroxypropylmethylcellulose, titanium dioxide, macrogol, polysorbate 80, and maltodextrin.
Diclofenac free acid 46.5 mg dispersible tablets (equivalent to 50 mg as sodium salt) marketed as Voltarol® contain microcrystalline cellulose, croscarmellose sodium, sodium starch glycollate, sodium saccharin, cellulose, hydrogenated castor oil, talc, silicon dioxide, erythrosine, aluminium oxide, and blackcurrant flavor.
Each of these commercially marketed products employ traditional disintegrants such as croscarmellose sodium, crospovidone and sodium starch glycolate to aid in the break up of the compacted mass and expose the active ingredient to the solvent. The formulations are not designed to expose the active ingredient by dissolving the excipient base. Even the diclofenac potassium product marketed as Voltfast, which is marketed based on its fast onset of action, contains excipients such as calcium phosphate that are practically insoluble. While Voltfast® does contain saccharose, which is very soluble in water, this ingredient is only present only in a minor amount in the outer film coating.
Mannitol is a water soluble, non-hygroscopic diluent that produces a semi-sweet, smooth, cool taste, that has been used for in chewable tablet formulations prepared by direct compression and orally disintegrating tablets (ODTs). Sangekar et al., J. Pharm. Sci., vol. 61, pp. 939-944 (1972). Joshi et al. report that mannitol is often preferred over lactose because of its low hygroscopicity, drug compatibility, compressibility, sweetness, and relatively slower dissolution kinetics. Joshi et al., Pharmaceutical Technology (June 2004).
Adkin et al. studied the effect of different concentrations of mannitol in solution on small intestinal transit, in Pharmaceutical Research, Vol. 12, No. 3 (1995) and Jnl. Pharm. Sci., Vol. 84, No. 12 (1995), and determined that mannitol reduced the transit time through the small intestine for solutions containing mannitol. According to the authors, this reduced transit time had a significant potential for reduced biological uptake, especially for drugs absorbed through the small intestine such as cimetidine.